Does OpenAFS not solve your problem in some way? A little more context would be helpful.
The main reason we chose OpenAFS was the security model. However, from what I've read it seems to be based on Kerberos 4, which is out-of-date and has problems. It's also difficult to maintain a OpenAFS cell and requires a separate Kerberos authentication server.
I'm basically looking for a more modern DFS that implements better user-based security.